Nightjack's blog is, as its author put it rather beautifully yesterday, "slowly melting away as it drops off the edge of the Google cache". Nightjack has gone, too, exposed by the Times as Detective Constable Richard Horton from the Lancashire Constabulary, a once-anonymous blogger brought down by his quality writing.

If his accounts of frontline police life had been less brilliant, Mr Horton would not have found a readership among people curious to learn what it is like to enforce the law on a public that resents enforcement, or won an Orwell prize for political writing, or had his identity pieced together by a curious journalist. He would have been like every other blogger who starts typing thinking that a false name offers privacy. Instead he found himself in the high court yesterday, fighting and losing a battle that has alarmed bloggers everywhere. Justice Eady, who heard the case, agreed that many of them would be horrified to learn that the law did not protect their anonymity. But, he said, "blogging is essentially a public not a private activity". The Times was entitled to publish Nightjack's real name if it wanted to.

This ruling was as inevitable as it was unwelcome. The fact that Mr Horton wrote on the internet cannot be a reason in itself to expect special protection. He chose to put the facts that led to his exposure into the public domain. But the outcome marks a painful coming of age for the web. Bloggers have prided themselves on breaking convention - standing outside the world of traditional media and the rules applied to it by the courts. Now that illusory sense of freedom has gone.

With it will vanish some of the more fascinating and useful online writing. Mr Horton's blog expanded the public's understanding of policing, as he could not if he had told his employers what he was up to and published a sanitised account of life on the beat. At their best, blogs such as Nightjack, or the Civil Serf who revealed life in a Whitehall office before also being exposed, made the public services more open, and improved debate about how they should run. Anonymity was essential to their ability to do this.

Nightjack's case was complicated by the fact that he had described aspects of investigations, in breach of his terms of employment. But the Times could not show that harm had been caused by this. All sorts of journalism relies on information provided anonymously by sources whose employers would rather they said nothing. If Mr Horton had whispered news of a scandal to a paper, it would have printed it. Because he communicated directly, he was exposed. It was a blow to new media, on behalf of the old.